On 8/20/26 8:41 AM, Guopeng Zhang wrote:
From: Guopeng Zhang <[email protected]>effective_xcpus includes CPUs granted to valid child partitions. Passing the whole mask to isolated_cpus_update() during a root-to-isolated or isolated-to-root change applies the parent's new state to child-owned CPUs as well. Build a mask of CPUs owned by the partition by subtracting the effective_xcpus of valid children. Use this mask when updating isolated_cpus for a partition type change. Fixes: 11e5f407b64a ("cgroup/cpuset: Keep track of CPUs in isolated partitions") Signed-off-by: Guopeng Zhang <[email protected]> --- kernel/cgroup/cpuset.c | 30 ++++++++++++++++++++++++++++-- 1 file changed, 28 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 2538faac9aba..468272baadb2 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2155,6 +2155,30 @@ static void compute_partition_effective_cpumask(struct cpuset *cs, rcu_read_unlock(); }+/*+ * Compute CPUs owned directly by a partition. + * + * effective_xcpus includes CPUs granted to valid child partitions. Exclude + * those CPUs when changing only this partition's type. + */ +static void compute_partition_owned_cpumask(struct cpuset *cs, + struct cpumask *owned_cpus) +{ + struct cgroup_subsys_state *css; + struct cpuset *child; + + lockdep_assert_held(&cpuset_mutex); + cpumask_copy(owned_cpus, cs->effective_xcpus); + + rcu_read_lock(); + cpuset_for_each_child(child, css, cs) { + if (is_partition_valid(child)) + cpumask_andnot(owned_cpus, owned_cpus, + child->effective_xcpus); + } + rcu_read_unlock(); +} + /* * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree * @cs: the cpuset to consider @@ -2990,8 +3014,10 @@ static int update_prstate(struct cpuset *cs, int new_prs) } else if (old_prs && new_prs) { /* * A change in load balance state only, no change in cpumasks. - * Need to update isolated_cpus. + * Need to update isolated_cpus for CPUs owned by this partition, + * excluding CPUs distributed to valid child partitions. */ + compute_partition_owned_cpumask(cs, tmpmask.new_cpus); if (((new_prs == PRS_ISOLATED) && !isolated_cpus_can_update(cs->effective_xcpus, NULL)) || prstate_housekeeping_conflict(new_prs, cs->effective_xcpus)) @@ -3030,7 +3056,7 @@ static int update_prstate(struct cpuset *cs, int new_prs) if (!is_partition_valid(cs)) reset_partition_data(cs); else if (isolcpus_updated) - isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus); + isolated_cpus_update(old_prs, new_prs, tmpmask.new_cpus); spin_unlock_irq(&callback_lock);/* Force update if switching back to member & update effective_xcpus */
Your use of tmpmask.new_cpus in isolated_cpus_update() can be problematic. isolcpus_updated can be set when an isolated partition is enabled or disabled. In both cases, tmpmask.new_cpus can be used temporarily. So the content of this temporary cpumask may not be what we want to pass into isolated_cpus_update(). I will suggest you only use tmpmask.new_cpus if it is determined to be coming from partition state transition instead of enabling/disabling of partition.
Cheers, Longman
